1. Field of the Invention
This invention concerns a device and a method to enable disconnection of a tool and a pipe string. More particularly, it concerns a disconnection device to be used especially in connection with coiled tubing operations, in which the connection part attached to the pipe string is of an external transverse dimension that may be equal or smaller than that of the pipe string. The invention also comprises a method of effecting the disconnection.
During coiled tubing operations, and especially when using a coiled tubing in for example a borehole, a tool attached to the pipe string may become solidly stuck in the borehole to a degree rendering the pipe string useless for pulling it loose.
Pipe strings are commonly provided with a disconnection device enabling disconnection of the tool and the pipe string, after which the pipe string and the disconnected part of the tool may be retrieved from the borehole. The tool may subsequently be pulled up using fishing tools.
Known disconnection devices are generally formed with a transverse dimensions larger than that of the pipe strings onto which they are attached. Due to this situation, there can be a problem pulling the part of the connection device connected to the pipe string through restrictions located close to the surface. In the past, this problem as been solved for instance through the use of an explosive charge that is introduced into the pipe string immediately above the connection, after which the connection device part is disengaged through blasting from the pipe string. The pipe string then may be pulled up to the surface.
Prior to the positioning of the charge, any hydraulic lines and cables present in the pipe string have to be disconnected and retracted to the surface.
2. Description of the Related Art
The object of the invention is to remedy the disadvantages associated with the prior art.
The object of the invention is achieved through features disclosed in the specification below and in the subsequent claims.
In accordance with one aspect of the present invention there is provided a disconnection device for disconnecting a tool and a pipe string, the device comprising a first connection part releasably connected to a second connection part by means of a locking device and a release object, wherein at least a section of the release object is soluble.
At least in preferred embodiments, a first connection part having an outer transverse dimension equal to or less that that of the pipe string is connected, possible via intermediate parts, to the lower end section of the pipe string. By means of an axially split connector ring of known type, the first connection part is releasably connected to a second connection part. The second connection part is connected, possible via intermediate parts, to a tool.
The split connector ring is maintained in its locking position by means of a pre-stressed locking object aimed in the direction of opening, a release object preventing the locking object from shifting away form its locking position.
At least in preferred embodiments, a first connection part having an outer transverse dimension equal to or less than that of the pipe string is connected, possible via intermediate parts, to the lower end section of the pipe string. By means of an axially split connector ring of known type, the first connection part is releasably connected to a second connection part. The second connection part is connected, possible via intermediate parts, to a tool.
During pipe string operations of the stated type, at least one hydraulic pipe is commonly introduced down to the tool inside the pipe string. By connecting this hydraulic pipe to the release object, the object may be dissolved for instance upon pumping acid down through the hydraulic pipe.